Previously, there has been an image pickup apparatus having a function of a live view mode. In the live view mode, an object image can be confirmed by sequentially outputting image signals continuously read out of a solid-state image pickup element such as a CCD or a CMOS sensor to a display device such as a liquid crystal display.
Patent Literatures 1 and 2 disclose a configuration where phase difference focus detection is performed by arranging focus detection pixels where pupil division function is given to a part of light receiving elements (pixels) of an image pickup element between imaging pixels at predetermined intervals. Since the area where the focus detection pixels are arranged corresponds to a defect part of the imaging pixel, Patent Literatures 1 and 2 disclose generating image information by performing an interpolation based on peripheral imaging pixel information.
In the image pickup apparatus having the image pickup element such as a CMOS sensor, a rolling electronic shutter which reads a screen every line is used. Therefore, when the live view mode is functioned by using the image pickup apparatus, there is a problem that a horizontal-striped flicker (a line flicker) is generated in an imaging screen. The flicker is generated depending on an accumulation time of the image pickup element, a frame frequency of the image pickup element, and an alternate lighting cycle of a fluorescent when a moving image of an object is displayed or recorded under a light source directly lighted by using a commercial power source such as under the illumination of the fluorescent. When the accumulation time of the image pickup element is set so as to be an integral multiple of the lighting cycle of the fluorescent to align an exposure amount every line, the influence of the flicker can be reduced.
However, a dedicated control is necessary for both cases of an area flicker and the line flicker. Therefore, it is necessary to detect the existence or nonexistence of the flicker at a certain timing to control the flicker in accordance with the detection result (flicker elimination mode). Patent Literature 3 discloses a method of performing highly-accurate autofocus detection by reducing the influence of the flicker.